syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P16176/1:b..l
	(detected by 0, t=10502 jiffies, g=96957, q=423 ncpus=2)
task:dhcpcd-run-hook state:R  running task     stack:22456 pid:16176 ppid:3306   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5241 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6558
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6870
 irqentry_exit+0x53/0x80 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:653
RIP: 0010:debug_lockdep_rcu_enabled+0x25/0x30 kernel/rcu/update.c:281
Code: cc cc cc cc cc 31 c0 83 3d 67 49 f3 03 00 74 1d 83 3d f2 7c f3 03 00 74 14 65 48 8b 0d 04 be 5b 75 31 c0 83 b9 dc 0a 00 00 00 <0f> 94 c0 c3 cc cc cc cc cc cc cc 48 8b 3c 24 e8 57 fb ff ff 66 90
RSP: 0018:ffffc900057173b8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff88802866d4b8 RCX: ffff88804b861dc0
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000006
RBP: ffffc900057175b0 R08: ffffffff8a9dbd86 R09: ffffffff8a9dbc0b
R10: 0000000000000003 R11: ffff88804b861dc0 R12: 1ffff92000ae2e97
R13: ffffc900057174b8 R14: ffff88801db46900 R15: ffff88807e61ee58
 mt_slot lib/maple_tree.c:814 [inline]
 mas_slot lib/maple_tree.c:847 [inline]
 mt_validate_nulls lib/maple_tree.c:7187 [inline]
 mt_validate+0x4fe9/0x5ad0 lib/maple_tree.c:7243
 validate_mm_mt+0x165/0x670 mm/mmap.c:295
 __split_vma+0x32/0x530 mm/mmap.c:2344
 do_mas_align_munmap+0x953/0x15f0 mm/mmap.c:2491
 do_mas_munmap+0x246/0x2b0 mm/mmap.c:2640
 mmap_region+0x8e6/0x1fa0 mm/mmap.c:2688
 do_mmap+0x8c5/0xf60 mm/mmap.c:1425
 vm_mmap_pgoff+0x1ca/0x2d0 mm/util.c:520
 ksys_mmap_pgoff+0x4f5/0x6d0 mm/mmap.c:1471
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f60339f6b74
RSP: 002b:00007ffcd0c36d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007ffcd0c36de0 RCX: 00007f60339f6b74
RDX: 0000000000000001 RSI: 0000000000025000 RDI: 00007f6033707000
RBP: 00007ffcd0c37100 R08: 0000000000000003 R09: 000000000002e000
R10: 0000000000000812 R11: 0000000000000246 R12: 00007f60339da570
R13: 00007ffcd0c37188 R14: 000000000002d9c6 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10188 jiffies! g96957 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:26712 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5241 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6558
 schedule+0xbf/0x180 kernel/sched/core.c:6634
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:567